As disclosed in Patent Literature 1, a turbocharger (electric supercharger) including an electric drive device is known. The drive device has a motor and rotates a shaft and a compressor impeller together. The shaft is supported by a bearing assembly. A labyrinth seal is provided on a rear surface side of the compressor impeller. The labyrinth seal includes a concentric ring bulged in three steps. This concentric ring meshes with a ring formed on a rear surface portion of the compressor impeller. These form a meandering passage (labyrinth) without being in contact with each other.